You will not for a long period of time to sell your coins , only that you will monitor the price value of coins in the market, in time when the market turns greener then you can sell your coins , but when you look that the price value is going down you can hold your coins in your wallet and wait for the right time.
What I do is I depend on my needs of money, if I need money in urgent situation, I sell part of my coins to use on my needs, even the price in the market is low, I still sell it due to my urgency needs, but I make sure that I still have coins to hold so in the future it still can earn.